The experiments described in this proposal are addressed to: (1) the revelation of the central site(s) of morphine's 'analgesic' action; (2) a comparison of morphine-induced and electrically-induced analgesia at coincident brain loci; (3) an evaluation of the relationship(s) between various neurotransmitters and the analgesias induced by morphine and focal brain stimulation (FBS) via push-pull perfusion of the brain; and (4) electrophysiologic (single unit) and microiontophoretic examination of the effect(s) of morphine and FBS-induced analgesias at relevant brain areas determined and warranted by previous experimentation (i.e., 1, 2 and 3 above). The proposed experiments include: (1) the intracranial administration (35 gauge cannulae) of morphine as well as centrally acting, 'non-analgesic' agents (e.g., chlorpromazine, chlordiazepoxide, pentobarbital, etc.); (2) the evaluation of drug and FBS effects in several analgesiometric tests integrated at different levels of the CNS (e.g., standard analgesiometric hot plate and tail flick tests and noxious trigeminal stimulation escape test); and (3) dissociation of the sensory/discriminative from the motivational/affective components of the 'analgesias' induced by morphine and FBS via conditioned response suppression and signal detection paradigms. The purpose of the proposed studies are to elaborate on the central sites and mechanism(s) of morphine's analgesic action.